Here's why:
* Cells are the smallest unit that can carry out all the processes necessary for life. They have their own DNA, can reproduce, and can perform metabolic functions.
* Tissues are groups of similar cells that work together to perform a specific function. For example, muscle tissue is made up of muscle cells that work together to allow movement.
* Organisms are made up of different types of tissues working together. Organs are made up of different tissues, and organ systems are made up of different organs.
So, while tissues are important components of living organisms, they are not the fundamental unit of life. That distinction belongs to the cell.
